The present invention relates to a method of manufacturing a casting mold of a flowable, binder-free backfilling material, stabilized by negative pressure.
It is known to utilize lost forms of foamed synthetic plastic material for manufacturing of cast parts. These forms are surrounded by sand provided with binding medium. Into the foamed synthetic plastic form molten metal is introduced so as to vaporize the form and to occupy its place. This technique, known as the full mold process, is widely utilized. However, it has the disadvantage that the outer face of the final cast part is rough and many cores are necessary.
It has been proposed to pour the foamed synthetic plastic form in a binder-free sand. This method has the disadvantages that during the vaporization of the foamed synthetic plastic material a strong shrinkage of the form takes place and thereby the dimensions of the cast parts do not correspond to the initial dimensions of the form.